Under the 3GPP standards, a NodeB (or an eNB in LTE) is the base station via which mobile devices connect to the core network. Recently the 3GPP standards body has adopted an official architecture and started work on a new standard for home base stations (HNB). Where the home base station is operating in accordance with the (Long Term Evolution) LTE standards, the HNB is sometimes referred to as a HeNB. A similar architecture will also be applied in the WiMAX network. In this case, the home base station is commonly referred to as a femto cell. For simplicity, the present application will use the term HNB to refer to any such home base station and will use the term NodeB generically to refer to other base stations (such as the base station for the macro cell in which a HNB operates). One or more HNBs will provide radio coverage (for example, 3G/4G/WiMAX) within the home and will connect to the core network via one or more suitable public networks (for example via an ADSL link to the Internet) and in the case of the 3GPP standards, via an HNB gateway (HNB-GW) which will aggregate traffic from the one or more HNBs.
An HNB may be configured to operate using one of a plurality of access modes, namely: ‘closed’ in which the HNB operates as a closed subscriber group (CSG) cell; ‘hybrid’ in which the HNB operates as a CSG cell where at the same time, non-members are allowed access; and ‘open’ in which the HNB operates as a normal (non-CSG) cell.
A mobile device that is a member of multiple CSGs may relocate, following successful access control, from a first home base station that is a member of a first CSG to a second home base station that is a member of a second, different, CSG.